Describing and understanding the behavioral repertory of a species, the development of the repertory and interspecific comparisons, all from an heredity-experience perspective, are the long-term objectives of this research -- the behavior-genetic analysis of species which now present the unique opportunity literally to manipulate experimentally both heredity and experience in a significant way. For the first time anywhere and at present only in this laboratory is it possible actually to analyze the genetic correlates of relatively simple learning processes validly and reliably measured in single individuals, the specific aims. A behavior-genetic component analysis of two dipteran species (Drosophila melanogaster and Phormia regina) is being done, using as phenotypes both experimentally modifiable (conditioning/learning and excitation) and instinctive or relatively unchangeable (taxes) behaviors. Working with geotaxis and with conditioning of a component of feeding behavior, the proboscis extension reflex, conditioned behavior is being analyzed into associative and nonassociative components (constructs) and individual differences are being measured in the expression of the behavior and of its components, then gene correlates of the behavior and of the components are being identified. Long-term divergent selection of D. melanogaster for geotaxis has permitted the present analysis of the genetic changes accompanying the evolution of instinct and of the rise of reproductive (ethological) isolation between evolving populations. The relevance of this research extends well beyond these dipteran species being used as models for behavior-genetic analysis with complex behaviors as phenotypes. Though mental illness, from alcoholism to manic-depression, schizophrenia and retardation, is now attributed by so many, at least in part, to heredity, nobody knows how to study inherited behavior. The present analyses of Drosophila (and other Diptera) are revealing much about what is involved in the behavior-genetic analysis of any diploid, bisexual, cross-fertilizing species, including man. These studies yield an important and unique picture of the role of heredity and experience -- identified genetic factors and specific training procedures -- in the evolution and expression of behavior.